1. Field of the Invention
The present invention relates to a method of managing electric power in a network within a dwelling. It also concerns a system for its implementation.
2. Description of the Related Art
Management of electric power in a network within a dwelling involves limiting the total power drawn from the mains system to a value which is less than the sum of the powers of all the appliances installed in the building without the user being inconvenienced by this limiting.
The term "dwelling" is construed as any self-contained or multi-occupancy premises for private, public or professional use. The term "network" is construed as any home network which uses any communication medium. In the discussion below, it is to be understood that the terms "appliances" and "electrical devices" are to be taken as synonymous.
For purchasers of a home network, the aim is to reduce their expenditure commitment to their electric power distributor. The reduction in costs achieved by power management is directly related to the tariff policy of the electric power distributor. If the cost of a subscription is linked to the amount of power signed up for, power management makes it possible to opt for a subscription for less power than that which would normally be needed. If the price of energy depends on the total power supplied to the installation, power management makes it possible to avoid reaching tariff rates beyond which energy becomes more expensive. In addition to its economic benefits, power management is also justified by the extra convenience it provides by eliminating the risk of untimely tripping due to overloading the mains system.
Power management is currently generally achieved by using a special electrical communication and control installation which requires special-purpose wiring and is not particularly upgradeable or by using the indoor mains system directly as a communication medium by using the well-known carrier current technique.
A method of controlling load disconnection/reconnection which uses look-ahead techniques for a home network is known from European patent application EP-A-0372961 filed on behalf of HONEYWELL INC. An electric power distribution system consisting of a control unit designed to monitor the power which the system can deliver and the power demanded by loads for their operation is also known from British patent application GB-A-2071438 filed on behalf of CENTRO RICERCHE FIAT SPA.
All these methods have the drawback of requiring that systematic power measurement be carried out and involve comparison between measured, global or partial power and a power setpoint. In addition, the management units of systems disclosed in the above mentioned documents generate load shedding/reconnection commands according to predetermined priority criteria without any possibility of compromise or negotiation between managements units and disconnectable appliances. In addition, power management systems according to the prior art use additional switches outside the controlled appliances and require special-purpose wiring.